Catabolism of the apolipoproteins of HDL in control and nephrotic rats.
125I-labeled high density lipoprotein (HDL) from control rats, or from rats made nephrotic by puromycin aminonucleoside, was injected into control or nephrotic rats. At 5 and 20 h, the amount and distribution of label remaining in apolipoproteins HDL, A-I, E, A-IV and the C apolipoproteins was measured after ultracentrifugal isolation of HDL and SDS-polyacrylamide gel electrophoretic separation of each apolipoprotein. There were no significant differences in the removal rates of apolipoprotein HDL or of the individual apolipoproteins when the removal of HDL of controls was compared to HDL of nephrotics. HDL from nephrotic rats contains less than 10% of either the apolipoprotein A-IV or apolipoprotein E content of control HDL, indicating that neither apolipoprotein A-IV nor apolipoprotein E play a significant role in determining the catabolic fate of rat HDL. In severely nephrotic animals the apoliprotein C content of HDL was reduced to 50% of control values and the apolipoprotein A-I content of HDL rose to 87% of the total apolipoprotein. The individual apolipoproteins of HDL from either nephrotics or controls were catabolized at the same rates irrespective of the degrees of nephrosis or altered HDL apolipoprotein composition. The apparent fractional catabolic rates for apolipoprotein HDL and for each of the apolipoproteins, determined after 20 h, did not differ from one another, and all were reduced by half in the nephrotic rats compared to the normal controls. These results support the concept that HDL is catabolized as a particle mediated by apolipoprotein A-I recognition, and they reinforce earlier work indicating that increased synthesis is the dominant factor responsible for increased plasma HDL concentrations in experimental nephrosis.
D000818:Animals; D016632:Apolipoprotein A-I; D001053:Apolipoproteins / Q000097:blood; D001054:Apolipoproteins A; D001056:Apolipoproteins C; D001057:Apolipoproteins E; D002784:Cholesterol / Q000097:blood; D008297:Male; D009401:Nephrosis / Q000097:blood*; D051381:Rats
D016632:Apolipoprotein A-I; D001053:Apolipoproteins; D001054:Apolipoproteins A; D001056:Apolipoproteins C; D001057:Apolipoproteins E; C022205:apolipoprotein A-IV; D002784:Cholesterol